Anecdotal evidence indicated an increase in red maples throughout Northeastern forests, but there was no hard evidence to back that up until Songlin Fei, assistant professor in the University of Kentucky's Department of Forestry, decided to delve into the matter. In two separate studies in collaboration with Penn State’s Kim C. Steiner, Fei first documented the proliferation of the tree in what had been primarily oak and hickory forests and then investigated the cause for the increase.